Effect of the syndesmotic screw on ankle motion.

The purpose of this study was to determine the effect of syndesmotic screw fixation on ankle motion. Eight unpaired osteoligamentous cadaver ankles were tested. The study quantified ankle flexion, talar tilt, ankle drawer, and tibiotalar rotation for each specimen using an MTS biomechanical testing system. Each specimen was tested under a 15-kg and a 70-kg axial load. The testing was repeated after the placement of a syndesmotic screw, a 4.5-mm cortical screw, in accordance with AO technique. There was a statistically significant decrease (P less than .05) in tibiotalar external rotation. There was no statistical difference in ankle flexion. There was a significant decrease in the anterior and the posterior drawer tests with the foot in plantar flexion. These were the most significant results. Syndesmotic screw fixation is used for the internal fixation of certain unstable ankle fractures. Opinions differ as to whether the screw should be removed at 6 weeks (prior to weightbearing) or left in place indefinitely. It was concluded that the syndesmotic screw should be removed prior to the return to full activity. Leaving it in place will contribute to abnormal ankle motion; this may result in local discomfort and a possible fatigue fracture of the screw.